1. Field of the Invention
The present invention relates to an oil pump mounting structure for mounting an oil pump to an engine, and more particularly to an oil pump mounting structure for mounting on an engine an oil pump adapted to be driven by the rotational force of a crankshaft.
2. Description of the Related Art
Oil is supplied to various places of an engine by an oil pump. Oil exhibits lubricating function, cooling function, rust preventing function and the like when it is supplied to the various places of the engine. For example, when the oil is delivered to rotating and sliding portions of the engine, the oil functions to lubricate those portions and reduces the frictional resistance thereat to thereby enable the engine to operate smoothly. In addition, when it is delivered to portions of the engine which are liable to be heated or rust, the oil functions to cool the portions or protect them against rust to thereby allow the engine to operate smoothly.
After having functioned to lubricate and cool those portions of the engine, the oil so delivered then drops in the form of droplets or flows down along walls of the portions and is finally collected in an oil pan which is an oil reservoir provided at a lower portion of the engine. Then, in an engine using a wet sump, the oil so collected in the oil pan is designed to be drawn up by the oil pump to be supplied again to the various portions of the engine.
Incidentally, conventionally known as an oil pump which plays such an important role is a crankshaft-driven type oil pump which is designed to connect to the crankshaft of an engine to be driven. This type of oil pump is designed in general to be fixed to the cylinder block with bolts which function as oil pump mounting portions. For example, JP-B-6-45628U discloses an xe2x80x9cengine with a balancer shaftxe2x80x9d in which a pump housing (an oil pump) is fixed to the cylinder block with bolts.
FIG. 5 is a view showing a conventional mounting structure for mounting this type of crankshaft-driven oil pump to an engine. In FIG. 5, denoted by reference numerals 102, 107, 110 and 111 and a reference character B are, respectively, a cylinder block, a crankshaft, a bearing cap, an oil pump and bolts. The oil pump 111 contoured by thicker solid lines in FIG. 5 is a trochoidal oil pump which has an inner rotor and an outer rotor, both not shown, which are profiled by a trochoidal curve and is adapted to draw oil through a time lag in rotation between the two rotors and supply it under pressure to required portions of the engine. The oil pump 111 is fixed to the cylinder block 102 with the bolts B. In addition, the oil pump 111 is designed such that the inner rotor is caused to rotate by virtue of rotational force obtained from the crankshaft 107 which is passed into the inner rotor.
In the mounting structure for the oil pump shown in FIG. 5, however, the oil pump 111 is fixed only to mounting portions on the cylinder block 102. On the other hand, as shown in FIG. 5, the oil pump 111 is constructed such that it extends (protrudes) downwardly of the cylinder block in order to draw oil from the oil pan (not shown). In this construction, the oil pump 111 is mounted only at an upper portion thereof to the cylinder block 102, which reduces the mounting rigidity and deteriorates the mounting balance, and thus the construction is not preferable as the mounting structure of the oil pump 111. In addition, in order to increase the mounting rigidity of the oil pump 111, as shown in FIG. 5, a construction is required in which the cylinder block 102 extends below the crankshaft 107, and this results in an increase in the overall weight of the engine or a reduction in degree of freedom in designing engines.
Then, a primary object of the invention is to provide a mounting structure for an oil pump which can solve the problems to thereby increase the mounting rigidity, as well as the mounting stability.
In view of the problems the inventors devoted themselves to study and paid their attention to an idea that the oil pump is mounted not only to the cylinder block but also a bearing gap, thus the invention having been completed.
With a view to attaining the object, according to a first aspect of the invention, there is provided an oil pump mounting structure for mounting a crankshaft-driven type oil pump to an engine, characterized in that oil pump mounting portions where the oil pump is mounted are provided on both a cylinder block and a bearing cap which support a crankshaft together with each other, whereby the oil pump is mounted on the engine via the oil pump mounting portions.
According to the construction, the oil pump mounting portions where the oil pump is mounted are provided on the bearing gap as well, whereby the oil pump is mounted to the engine both at the cylinder block and the bearing cap. Thus, the mounting rigidity and mounting stability of the oil pump to the engine can be increased. Note that in an embodiment which will be described later, mounting seats (bolt holes) which function as oil pump mounting portions are provided in the cylinder block and the bearing cap, so that the oil pump can be mounted to both the cylinder block and the bearing cap with bolts.
According to a second aspect of the invention, there is provided an oil pump mounting structure as set forth in the first aspect of the invention, wherein the oil pump mounting portions which are provided on the bearing cap are disposed between center lines of a pair of bolt holes through which bolts are allowed to pass to mount the bearing cap to the cylinder block on both sides of the crankshaft as viewed from the front of the crankshaft in an axial direction thereof.
According to the construction, the oil pump mounting portions are provided at portions of the bearing gap which have a certain strength. Consequently, the mounting rigidity and mounting stability of the oil pump to the engine can be increased. In addition, the necessity of enlarging the oil pump and the bearing cap can be suppressed. Note that the word, front, which is used in the claim as stating, xe2x80x9cas viewed from the front of . . . xe2x80x9d denotes a direction which is illustrated in FIG. 4B which depicts the embodiment of the invention which will be described later.
According to a third aspect of the invention, there is provided an oil pump mounting structure as set forth in the first or second aspect of the invention, wherein the bearing cap on which the oil pump mounting portions are provided is connected to an adjacent bearing cap by a connecting wall.
According to the construction of the third aspect of the invention, since the bearing cap on which the oil pump mounting portions are provided is connected to the adjacent bearing cap, the rigidity of the bearing gap can be increased. Thus, the mounting rigidity of the oil pump which is mounted to the bearing cap can also be increased. Note that rigidity can further be increased in the event that all the bearing caps are constructed to be connected to one another as described in the embodiment of the invention which will be described later.
According to a fourth aspect of the invention, there is provided an oil pump mounting structure as set forth in the third aspect of the invention, wherein the oil pump mounting portions that are provided on the bearing cap are provided at a portion of the bearing cap where the connecting wall is connected to the bearing cap.
The portion of the bearing cap where the connecting wall is connected to the bearing cap is a portion having a high rigidity. According to the construction, since the oil pump mounting portions are provided at the highly rigid portion of the bearing cap where the connecting wall is connected thereto, the mounting rigidity of the oil pump which is mounted to the engine via the oil pump mounting portions can be inevitably increased.
In addition, when looking at the respective constructions of the invention from a different point of view, the mounting rigidity and mounting stability of the bearing cap to the cylinder block can be increased by mounting the oil pump to both the cylinder block and the bearing cap. In this case, the oil pump plays a role of reinforcement in mounting the bearing cap to the cylinder block.